Note: Descriptions are shown in the official language in which they were submitted.
CA 02956336 2017-01-26
A Composite Material Container and the Forming Method of its Composite
Material Layer
Technical Field
The present invention relates to a gas transportation technology, and in
particular, to a
composite material container and the forming method of its composite material
layer.
Background Art
Prior art is used to transport natural gas, hydrogen and helium and realize
transportation mainly by increasing storage pressure. With the development of
gas
industry, there is an increasing demand for pressure of gas storage
transportation
container.
The inner tank of high-pressure composite container (gas cylinder) produced
according to prior art is made of metal materials. In order to increase the
volume and
bearing pressure of composite container (gas cylinder), common method is to
use tip
spinning method with high-Pressure seamless metal tube to make inner tank.
Then
wrap a layer of high strength fiber material on the outer surface of inner
tank and
increase bearing pressure with traction of high strength fiber material. Prior
art may
cause cracks along fiber direction due to increasing pressure. With the
increase of
frequency of use and impact of specific environment, these cracks will tend to
spread
and may lead to cracking of the whole composite layer if it is serious.
In view of this, there is an urgent need for a new technology to effectively
reduce or
eliminate cracking of the composite material layer.
Contents of the Invention
It is therefore an object of the present invention to overcome the defects of
the prior
art, this present invention provides a composite material container which can
reduce
and even eliminate the cracking of the composite material layer and the
forming
method of the composite material layer.
To achieve the above-mentioned purpose, the present invention provides a
forming
method of composite material layer of composite container: a fiber is wrapped
around
the outer surface of inner tank at a predetermined angle to form at least one
composite
material layer. A layer of additive is added between composite material layers
and/or
on the inner surface of composite material layers and/or on the outer surface
of
composite layers to prevent cracking of composite material layer.
Further, the layer of additive is located between two composite material
layers.
Further, the additive is fabric or non-woven fabric.
Further, the additive is in the shape of fibrous, lamellar, flocculent and
block.
Further, the additive is made of metal or nonmetal material.
Further, the additive is made of fiber materials. The fiber materials are
composed of
one or more of the following materials: carbon fiber, glass fiber, aramid
fiber,
polyester fiber and metal fiber.
Further, the continuous fiber is wrapped along the outer surface of inner tank
in the
shape of ring.
Further, the continuous fiber is wrapped along the outer surface of inner tank
in the
spiral shape.
This present invention provides a kind of composite material container which
is
composed of an inner tank and composite material layer.
Description of Figures
The advantages and purpose of the present invention can be understood through
the
following detailed description of the present invention and drawings.
Fig. 1 is a schematic diagram of the present invention;
Fig. 2 is a schematic diagram of partial enlargement of the present invention.
Specific Mode for Carrying Out the Invention
The preferred embodiment is described as follows with diagram.
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CA 02956336 2017-01-26
Current composite material container (gas cylinder) is formed by hoop wrapping
fibers. Because the shrinkage rates between composite material layers wrapped
round
the built-in metal inner tank's outside surface and the built-in metal inner
tank are
inconsistent, the length of gas cylinder is extended in the process of
repeatedly filling.
The extension of metal material is better than that of composite material.
Then after
repeatedly filling, the extending length of metal is more than the length of
composite
material, which may cause cracking of circular direction on the surface of
composite
material. After increasing pressure, it will crack along fiber direction. With
increase of
using frequency and impact of specific environment, these cracks may tend to
extend.
If it is serious, it may cause cracking of the whole composite material layer.
Therefore,
the purpose of this present invention is to provide a kind of composite
material
container and forming method of composite material layer for prevention of
cracking
of the continuous fiber layer.
The present invention analyzes and calculates the matching longitudinal force
of fiber
circular wrapping and uses the enhancement technology in the process of
composite
material layer forming. When the composite material layer of gas cylinder
cracks
along the fiber direction in the process of increasing pressure and strength,
it provides
a pulling force perpendicular to cracking direction, so as to reduce cracking
and
long-term extension phenomenon.
As shown in Figure I, figure I is the schematic diagram of the structure of
the
composite material container involved in the present invention. The composite
material container can be a cylinder used for containing high pressure gas,
and can
also be a pipeline for high pressure gas, liquid or solid. Figure 1 is an
implementation
method. The container 2 is made of high quality seamless steel pipe, and two
cylinder
necks 3 in both sides of the steel pipe are processed according to the end
spinning
method. The built-in screw of the cylinder necks 3 is used to fix the front
end and
back-end plugs. Gas inlet and outlet valves are located in the front plug and
a safe
relief device is located in the back plug (it is not shown in the figure). In
the other
embodiment, the steel cylinder can also include an opening.
The outer surface of the steel cylinder 2 includes a composite material layer
I.
Composite material layer I is usually wrapped with continuous fiber along
circular
direction (a). Composite material layer 1 can only cover partial surface of
the steel
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CA 02956336 2017-01-26
cylinder 2, and can also cover the whole surface of cylinder 2, including the
outer
surface of the cylinder neck 3. As shown in figure 1, it is a typical circular
wrapped
composite material container. The circular winding is almost vertical between
continuous fiber winding angle and axial direction (b) of gas cylinder. The
problem of
circular winding cylinder is that: when the cylinder is filled with high-
pressure gas
and the contraction rates of metal tank and composite material layer are
inconsistent,
which cause cracking of circular direction (a) on composite material layer.
This
present invention provides a compensative force in longitudinal direction to
overcome
circular cracking.
In the other embodiment, the whole winding or wide angle winding method is
adopted
for the composite material container. When adopting this method, cracks will
appear
along the continuous fiber parallel direction. According to technical solution
offered
by this present invention, a compensative force in the vertical angle with
continuous
fiber is required to overcome cracks.
As shown in figure 2, it is the partial amplification of composite material
container in
the present invention. Different from the prior art, the composite material
layer 1
offered in the present invention includes an additive 11 besides continuous
fiber 10. It
increases a longitudinal force (b in figure 1) matching with circular pulling
force in
the forming process of composite material layer so as to reduce surface
cracking and
long-term crack extension phenomenon.
In a preferred embodiment, the continuous fiber 10 and additive 11 are
continuous
molding. That is a layer of additive II covered above or below a layer of
continuous
fiber 10. Additive II can be fabric and also be non-woven fabric. The fabric
is a
material which is formed by over two crossed and wound lines. Additive 11 can
be in
the shape of fibrous, lamellar, flocculent and block. If it is in the shape of
fibrous, the
additive 11 will be arranged longitudinally or extended with a certain angle
longitudinally.
Additive 11 can be made of carbon fiber, glass fiber, aramid fiber, polyester
fiber and
metal fiber. Carbon fiber (Carbon fiber, referred to as CF), is a new type of
fiber
material with high strength and high modulus fiber containing more than 95%
carbon
content. It is crystallite graphite material (through carbonization and
graphitizing)
made up of organic fibers, such as flake graphite crystallites, which are
piled along
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the axial direction of the fiber. Carbon fibers include, but are not limited
to
polyacrylonitrile-based carbon fiber, pitch based carbon fiber, viscose based
carbon
fiber, phenolic based carbon fiber and vapor grown carbon fiber. The
components of
glass fiber (glass fiber or fiberglass) are silica, alumina, calcium oxide,
boron oxide,
magnesium oxide and sodium oxide that are made through high-temperature
melting,
wire drawing, winding and weaving. The glass fibers include, but are not
limited to
non alkali glass fiber, C-glass fiber, high alkali glass. fiber, high strength
glass fiber,
high modulus fiber glass, high silica glass fiber, alkali-resistant glass
fiber and other
glass fiber. The full name of aramid fiber is poly- p- phenylene terephthamide
(Aramid fiber), which comprises PPTA and PMIA. The metal fiber is mainly made
of
metal (iron, iron alloy, steel, etc.) with technical methods such as cutting
off the thin
steel wire, cold-rolled steel belt shearing, ingot milling, or rapid
condensation of
liquid steel with the length/diameter ratio of 40-80 (when fiber cross section
is not
round, the converted equivalent cross section diameter will be adopted. )
The present invention also provides a forming method of composite material,
which is
achieved by adding fiber fabric in the process of winding composite material
around
the container. There are a wide range of fabrics such as carbon fiber fabric,
glass fiber
fabric, aramid fiber fabric or its mixed fiber as well as fiber fabric of
prepreg
resin matrix. First, when choosing fiber fabric, its surface infiltration
agent must be
compatible with the system of continuous fiber and resin system, so that in
the
process, fiber fabric, continuous fiber system and resin matrix make into a
whole
wrapped around the composite material layer and bear load as a whole. At the
same
time, in the long-term use process, stratification phenomenon of two materials
that
may affect service life of gas cylinder doesn't occur. Second, use horizontal
tile
method to overlay fiber fabric on some circular wrapped layer (may be bottom
or any
outer layer) that has been analyzed and calculated. Then use resin matrix to
impregnate it (the impregnation process can be omitted if choosing pre-
immersion
matrix resin). After overlaying, it shall be wrapped continuously and wrap the
overlaid fiber fabric around the wrapped layer. The fiber fabric overlaying
position
and number of layers can be analyzed, calculated and adjusted according to
actual
situation of the product.
The following will provide a method for producing composite material container
CA 02956336 2017-01-26
involved in this present invention. First, choose inner tank made of high-
pressure
seamless steel of suitable length according to designed capacity, then
position the
inner tank on a rotating axis and make high strength composite material layer
on the
surface of inner tank.
The composite material layer preparation steps: choose impregnating compound
compatible with continuous fibers used for wrapping and resin matrix, and use
fiber
fabric, continuous fiber used for wrapping, resin matrix, and surface
impregnating
compound to Corm a wrapped composite material layer as a whole through
solidifying.
Wrap fiber impregnated resin matrix around the circular container (inner tank)
according to parameters in form I.
No. Item Parameter
1 Winding speed <60m/min
2 Twisted fiber tension 240-300N
Glue liquid
3 35-50 C
temperature
4 Yarn width 18-20min
Requirement: without clipping glue on the
Gumming
surface of product, no adhesive
Form 1
Wind till a specific layer and then stop winding. Overlay the additive on the
composite material specific layer that is the layer n (n is a natural number).
Those
skilled in the art can set the location of specific layer according to
designed structure
size of gas cylinder, key points, line layout and the symmetry of the
structure.
Continuous fiber can be wrapped circularly on the surface of inner container
and also
can be wrapped in a certain angle (spiral winding). In the winding process,
you can
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overlay the additive in 900 direction with the circular direction or 30 with
the axis
direction of gas cylinder.
After completion of winding, adopt horizontal rotation staged temperature
curing
method for composite material, and cure 4-5 hours in the staged temperature
95¨
= 155 C. In the process, the gas cylinder should be rotated horizontally to
ensure
well-distribution of glue on the surface of gas cylinder.
Use hoop-wrapped composite cylinder (external diameter of inner tank: 406mm,
whole length: 2140mm) as the reference sample. Before filling, the straight
line length
of the gas cylinder is 1650mm, and after experiencing 15000 times of repeated
charge
and discharge under 25MPa work pressure, the straight line length of the gas
= cylinder's inner tank is 1670mm and metal liner length changes by 20mm.
But the
straight line length of composite material layer changes little. Because of
inconsistence of both lengths, composite material layer cracks obviously and
the
widest width of single circular crack can reach 7mm.
Use hoop-wrapped composite cylinder (external diameter of inner tank: 406mm,
whole length: 2140mm) as the reference sample. The straight line length of gas
cylinder's inner tank changes from 1650mm to 1670mm and metal liner length
changes by 20mm after experiencing 15000 times of repeated charge and
discharge
under 25MPa work pressure. The change rate of gas cylinder's inner tank is
1.2%. But
because of compensation for longitudinal force, the outer surface of hoop-
wrapped
composite gas cylinder filled with additives only has some evenly-distributed
circular
cracks and the widest width of each crack is less than 2rnm.
Industrial applicability
Compared with the prior art, the present invention provides composite material
container and forming technology of composite material layer. There is a
longitudinal
(axial) reinforcing effect within wrapped composite material layer to
effectively
prevent composite material cracking or crack extension. That can prevent
cracking or
cracking extension along fiber of wrapped composite layer in the long-time use
process and to some extent, stabilize the performance of container and
thereby,
= improve the safety of container in the use process.
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